1. Field of the Invention
The present invention relates to a novel polyamido-acid copolymer capable of forming a polyimide resin film excellent in adhesion and mechanical strength and a process for producing it.
2. Description of the Prior Art
Polyimide resins are excellent in electrical properties and mechanical strength and their use for, for example, protective films for the surface of semiconductor devices are attracting attention.
However, since generally polyimide resins are weak extremely in adhesion to inorganic materials, if they are used for protective films for the surface of semiconductor devices, there is a problem that the above properties of polyimide resins are not exhibited well enough.
To cope with this problem, introduction of various silane coupling agents has been studied and as a result the adhesion to inorganic materials has been improved.
However, if a siloxane skeleton is introduced in a polyimide resin, the adhesion to inorganic materials is improved but the mechanical strength drops disadvantageously.